Investigations are directed at host defense mechanisms and immuno-regulation in malaria and leishmaniasis, and the possible role of the schistosomal egg granuloma in regulation of hepatic fibrosis. Presently, research is aimed at: (1) spleen function in malaria immunity, (2) regulation of intracellular growth of leishmania in human macrophages, and (3) characterization of a fibroblast stimulating factor produced in vitro by schistosomal egg granulomas. In addition, clinical studies are covered by project Z01 AI 00141-02 FY 1979.